Non-human animals, expressing humanized CD3 proteins are provided. Non-human animals, e.g., rodents, genetically modified to comprise in their genome humanized CD3 proteins are also provided. Additionally, provided are methods and compositions of making such non-human animals, as well as methods of using said non-human animals.

Genetically modified non-human animals expressing human EPO from the animal genome are provided. Also provided are methods for making non-human animals expressing human EPO from the non-human animal genome, and methods for using non-human animals expressing human EPO from the non-human animal genome. These animals and methods find many uses in the art, including, for example, in modeling human erythropoiesis and erythrocyte function; in modeling human pathogen infection of erythrocytes; in in vivo screens for agents that modulate erythropoiesis and/or erythrocyte function, e.g. in a healthy or a diseased state; in in vivo screens for agents that are toxic to erythrocytes or erythrocyte progenitors; in in vivo screens for agents that prevent against, mitigate, or reverse the toxic effects of toxic agents on erythrocytes or erythrocyte progenitors; in in vivo screens of erythrocytes or erythrocyte progenitors from an individual to predict the responsiveness of an individual to a disease therapy.

Genetically modified rodents such as mice and rats, and methods and compositions for making and using the same, are provided. The rodents comprise a humanization of at least one endogenous rodent Tmprss gene, such as an endogenous rodent Tmprss2, Tmprss4, or Tmprss11d gene.

An siRNA conjugate having a structure as represented by formula (1) for inhibiting hepatitis B vims gene expression, comprising siRNA and a conjugated group, wherein the sense strand of the siRNA comprises a nucleotide sequence 1, and the antisense strand comprises a nucleotide sequence 2; the nucleotide sequence 1 and the nucleotide sequence 2 are, at least in part, reversely complementary to form a double-stranded region; the nucleotide sequence 1 and SEQ ID NO: 1 are equal in length and differ by no more than three nucleotides; the nucleotide sequence 2 and SEQ ID NO: 2 are equal in length and differ by no more than three nucleotides. The siRNA conjugate can specifically target liver cells and effectively solve the problem of siRNA delivery in vivo, and shows excellent activity and low toxicity to inhibit HBV gene expression while maintaining high stability of siRNA.

Provided herein are immnunodeficient mouse models engrafted with cells comprising a pathogen entry moiety, for example, for assessing pathogenic infection. The pathogen may be a virus, such as a respiratory virus.

Provided herein are methods and compositions for the production of hepatocytes from placenta stem cells. Further provided herein is the use of such hepatocytes in the treatment of, and intervention in, for example, trauma, inflammation, and degenerative disorders of the liver. Also provided herein are compositions and methods relating to combinations of nanofibrous scaffolds and adherent placental stem cells and methods of using the same in cartilage repair. Finally, provided herein are compositions and methods relating to nonadherent, CD34.sup.+CD45.sup. stem cells from placenta.

The present invention provides a mouse with liver damage, having a high degree of damage against the mouse's original hepatocytes while having a uPA gene in a heterozygous form, and a method for efficiently preparing the mouse. Specifically, the method for preparing a mouse with liver damage having the uPA gene in a heterozygous form comprises the following steps of: (i) transforming mouse ES cells with a DNA fragment containing a liver-specific promoter/enhancer and cDNA that encodes a urokinase-type plasminogen activator operably linked under the control thereof; (ii) injecting the transformed mouse ES cells obtained in step (i) into a host embryo; (iii) transplanting the host embryo obtained in step (ii) via the injection of the ES cells into the uterus of a surrogate mother mouse, so as to obtain a chimeric mouse; and (iv) crossing the chimeric mice obtained in step (iii), so as to obtain a transgenic mouse in which the DNA fragment is introduced in a heterozygous form.

Genetically modified non-human animals expressing human EPO from the animal genome are provided. Also provided are methods for making non-human animals expressing human EPO from the non-human animal genome, and methods for using non-human animals expressing human EPO from the non-human animal genome. These animals and methods find many uses in the art, including, for example, in modeling human erythropoiesis and erythrocyte function; in modeling human pathogen infection of erythrocytes; in in vivo screens for agents that modulate erythropoiesis and/or erythrocyte function, e.g. in a healthy or a diseased state; in in vivo screens for agents that are toxic to erythrocytes or erythrocyte progenitors; in in vivo screens for agents that prevent against, mitigate, or reverse the toxic effects of toxic agents on erythrocytes or erythrocyte progenitors; in in vivo screens of erythrocytes or erythrocyte progenitors from an individual to predict the responsiveness of an individual to a disease therapy.

A non-human mammalian model for human diseases or disorders comprising a non-human neutrophil depleted mammalian host engrafted with a human skin equivalent (huSE) and human immune cells.

A mouse with a humanization of the miL-3 gene and the mGM-CSF gene, a knockout of a mRAG gene, and a knockout of a mII2rg subunit gene; and optionally a humanization of the TPO gene is described. A RAG/II2rg KO/hTPO knock-in mouse is described. A mouse engrafted with human hematopoietic stem cells (HSCs) that maintains a human immune cell (HIC) population derived from the HSCs and that is infectable by a human pathogen, e.g., S. typhi or M. tuberculosis is described. A mouse that models a human pathogen infection that is poorly modeled in mice is described, e.g., a mouse that models a human mycobacterial infection, wherein the mouse develops one or more granulomas comprising human immune cells. A mouse that comprises a human hematopoietic malignancy that originates from an early human hematopoietic cells is described, e.g., a myeloid leukemia or a myeloproliferative neoplasia.